The fact that from the words PRO MARKETPLACE - you managed to make up an entire theory of a new MacPro.
Labeling this a theory is dubious. Apple didn't reportedly say anything in this account. He told Apple what to do. Like Apple has to do anything in choosing the content for their own presentations. It is not a rumor about Apple (or any of their products ). It a rumor about what someone's feedback to Apple was. Like feedback doesn't happen everyday at
https://www.apple.com/feedback/
That could mean anything. Could mean they are finally upgrading all the pro-software.
WWDC is just about the worse venue Apple should/could promote their prowess as an Application developer. Apple gathers up thousands of developers and spends time talking about how good an application developer they are. Implicitly, having the ability run over any of those developers businesses whenever they really wanted to. That is
not something Apple will want to draw attention to at WWDC. Apple's message is going to be focused on how they are an "insanely great" development partner, not competitor.
FCPX is already on a regular upgrade schedule. "Logic X" probably is waiting till 10.6 essentially gets de-supported and it is bit more flushed out than FCPX was at launch. Neither one of those is likely to coincide exactly with WWDC.
You can get more of an idea about the possible next MacPro from the the recent releases from both GPU vendors.
The primary market for these cards are the
currently deployed Mac Pros; not the new ones. Unless Apple moves to an embedded GPU in the next Mac Pro and creates a BTO that leaves all slots open ( some number between 1-4; likely 4 ), then most folks buying these 3rd party cards are going to be buying them as replacements. The vast majority of replacements are for relatively "old" cards, not cards just bought in the last month or so (along with brand new Mac Pro).
Throw on top of that the EU Market blackout where folks are being force to get extended life out of already deployed Mac Pro and the June 2012 "speed bump" that left GPUs back in the 2009 era, it would be kind of loopy if some vendors did not show up at this point to "put a finger in the dike". In fact, I suspect they were hoping that 10.8.3 would come out sooner so the (not be one of the longest x.x.(n+1) in OS X history.). Indeed the K5000 was announced by Nvidia back in September 2012 and was targeted for 2012 release:
".. The Quadro K5000 for Mac is slated to begin shipping "later this year" from resellers and system integrators ..."
http://arstechnica.com/apple/2012/09/nvida-announces-kepler-based-quadro-k5000-gpu-for-mac-pro/
The eligible cards in a new Mac Pro are likely going to cover approximately the same performance range as these two new cards 7950 and 680 at approximately the same prices. Relatively few folks are going to buy a Mac Pro with one of those cards and then yank it out for one of these.
(Both Nvidia and AMD are largely just rebadging desktop GPU cards for release this year. Limited clock speed bumps of the same architectures. Any new Mac Pro would be using a card with same arch if release anytime inside of 2013.)
The only way new Mac Pros drive a significant upside to 3rd party cards is if there are no removable GPU PCI-e cards in the new Mac Pro and the normally occupied slot is empty. It shouldn't be hard for retailers to price 3rd party cards with some discounts to be lower than Apple's prices which carry Apple's mandatory 30+% mark-up. That would be a viable additive market for 3rd party cards. GPU cards would be in the same category as RAM, HDDs, SDDs, that you only buy from the Apple BTO site if you have copious money to "gift" to Apple or laboring under some "single purchase order" restrictions.
It's going to be the same size, with nothing more than a standard spec jump. It'll only seem like such a vast improvement because they have done nothing for 3 years.
It is likely to be a move to the evolutionary equivalents because that is exactly what has happened in the past. Apple could adjust the size a bit if there is a functional equivalent that gets the same performance class in a small or different dimensioned system.
The CPU and GPUs that are on cards will likely be a standard spec jump. An embedded GPU is likely going to be much closer to the class that has gone inside of MBP and iMacs than what has relatively been placed on PCI-e cards for previous Mac Pro. Moore's Law will enable these to be about as fast as some older cards, but won't be a med-high end 3D performance leader. It likely will be there in part to enable Thunderbolt. An embedded GPU also enables a slightly lower selling price which the Mac Pro also needs (something closer to the $2,000 border with iMac ).