I get the enthusiasm.  I really do.  But, methinks Z is juggling a few more variables in regards to the 2012 rotation.
Paxton, at this point, has 112.2 minor league innings, (95 in 2011).  They were outstanding minor league innings ... but, 56 in A and 39 in AA is still not much of a sample.
Walker has 103.2 innings with 96.2 in 2011 ... at Clinton.
Hey!  The Big Guy rushed Pineda into the rotation in April of 2010, of course.  Buuuut ... Pineda had 404 total minors innings, including 77 in AA and 62 in AAA before winning the #5 slot out of ST.  Then again, Pineda's competition for that slot was ... Nate Robertson?!?  I really don't remember.
Z has shown great flexibility for pushing someone that he believes HAS moved it up a notch, (Seager, Peguero, Lueke).  But, he's also shown the ability to admit when he has overreached and returned guys to the minors, (Lueke) for additional work.
Honestly, I think the odds of Walker reaching the majors before September is zero.  I just don't think Z is going to immediately power flush Beaven and Furbush so casually.
I think the odds of Vargas missing the rotation in April are effectively zero (barring injury).  If I had to guess right now, I'd say there are two open slots that Beaven, Furbush and Hultzen are competing for. 
My view is that Z is likely going to be VERY squeamish about having players skip AAA completely.  I think Z understands that there are "organizational" benefits to making even (maybe especially) the bonus baby talents showcase their talents at multiple levels.
One thing that is rice paper fragile is maintaining an ORGANIZATIONAL culture that demands EVERYONE prove themselves through hard work and performance on a daily basis.  For me there is absolutely zero difference in terms of the organizational detriments of "veteran entitlement" vs. "prospect entitlement".  The key word is entitlement.  You entitle anybody, you have negative blowback.  Doesn't matter if you're a future Hall of Famer (Griffey, Ichiro), or top draft pick, (Ackley, Hultzen). 
Ackley wasn't hitting 1000 in AA and AAA ... but almost every comment I read from teammates was filled with awe and respect.  Even though the numbers weren't there ... by playing beside the man, all the other players got an appreciation of WHY he was so highly regarded.  And Ackley wasn't pouting or grousing about his time in the minors - he spent the time working his butt off.  It is likely that Ackley's time in the minors was more beneficial to the entire minor league development than an extra hundred ABs in the majors would've been to his career.
This isn't to say it's completely out of the question for Z to hopscotch one of these guys into the rotation.  But, three?!?  I don't see it happening.
I'm thinking Furbush is a repeat of Olsen ... but, heck, if Furbush can get his gopher problem under control, he's got the stuff and control to be a valuable asset.  Beaven looks like a Doug Fister re-run in a number of ways.
I could also see Z deciding Walker, Paxton and Hultzen are all not ready and Beaven and Furbush aren't good enough and going out and doing a one year rental or reclamation pickup for the rotation, (like the Yankees did with Garcia).
I think one 'could' make the rotation in April, but that is not a certainty.  I think it likely that another will be brought up during the year, (depending on injury or subpar performance).  But, mostly I think (based on past experience), these guys will probably need to throw about 70 innings in Tacoma before they'll get the call to the Show.

"major league sources say"
Let's hope he would yield gracefully to the guys whose dads are younger than him.  He has 267 wins, so 300 is not a realistic goal.  That's good, actually, because it wouldn't be a distraction or rationale to give him more starts than he ought to.
Got a take on Jamie@49 Doc or anybody?
+++
I had Paxton as the #1 overall prospect, but I moved Hultzen ahead of him once it became clear that Hultzen really does throw 93 with precision (pitch after pitch after pitch) and can get to 95.
It's still a close call, but comparing Pineda, Hultzen and Paxton  using BaseballCube.com (which has college stats) the only thing about any of the three that gives one pause is Paxton's walk rate.  Paxton has been under 3.0 BB/9 only once. As a college junior it was 2.3 (but that year he also spiked in HR/9 at 1.26).
He has a higher WHIP as a result and, therefore, seems a little more likely to give up some big innings.
Hultzen and Pineda have never been over 3.0.  I would put the power/precision combo slightly ahead of the guys with a little less precision, which is why I'm also very excited about Campos and his 1.4 BB/9 rate in Everett.
But, cripes, they're all awesome.
And, notice that Morosi tosses Forrest ("something of a revelation") Snow (and/or "this year's Tom Wilhelmsen out-of-nowhere guy") right into the mix with Pax and Hultz, and it's probably "major league sources" saying that, too.

Moyer is so crafty, he keeps his own book of hitters, and updates it daily.  The young whippersnapper pitching staff could learn something from having him around.
The Mariners should sign him, and then add him to the coaching staff when his old bones start to creak.  He can do spot starts on days that air pressure is high.
Not much is as enjoyable as seeing Moyer's grayed, grizzled and cantankerous face malevolently smirking at another hitter who just struck out on his changeup.
The problem is, can a rotation be too lefthanded?  We have Felix and Pineda as the only righties if Beavan loses out.  Is it okay to have three lefties and two righties?  Does that violate a rule of baseball, or a law of sabermetrics or anything?