So speculatively speaking:
392 History:
2006 SEMA - Debut - 392 V8 Engine Crate Concept 525 hp / 510 tq
2010 SEMA - Release - 392 N/A V8 Challenger IE 470 hp / 470 tq
V10 History:
2008 SEMA - Debut - 512 V10 Challenger Concept 600 hp / 560 tq
2010 SEMA - Release - 512 V10 Challenger Drag Pak 600 hp / 560 tq
426 History:
2010 PRS - Debut - 426 Aluminum V8 Crate Engine 540 hp / 530 tq
Unknown
So let's look at what the competition has been doing.
2011 392 - 6.4L N/A 470 hp / 470 tq
2012 ZL1 Camaro - 6.2L Supercharged 550 hp / 550 tq
2013 Shelby GT500 - 5.8L Aluminum Supercharged 600+ hp projected
Dodge has already proven that they can get the Challenger to be a 600+hp monster in Drag Pack form, probably where it should be; on the track not on the street. Ford is now catching up by methods of supercharging to meet up with what Dodge has accomplished, however, they are more targeted for autocross rather than 1/4mi races.
Speculation
Mopar408's 392 w Maggie Build - 6.4L 630 rwhp / 645 rwtq
2010 SEMA - Edelbrock debuts Hemi Supercharger
Edelbrock’s E-Force Boosts New HEMI Horsepower - StreetLegalTV.com
So we look at the competition flying away with Supercharged engines and Dodge/Mopar sticking with Naturally Aspirated solutions.
The aftermarket for Dodge/Jeep have proven that a 392, 426 and 440 Hemi are possible solutions (forged block, upgraded internals) along with a supercharger.
So we look at now, would a 426 be reasonable with 540 hp / 530 tq or would Dodge look at the possibility of supercharging the 392 that has the capability of 600+hp. From a cost/market standpoint, the supercharging route seems the better way to go. A $6000-7000 part upgrade with tuning from factory to put the current 392 in the $54000 range. The output is much better than the 426 and the transmission capability is already backed by the Tremec 6-speed. Internals would need to be upgraded. From an engine longetivity standpoint, the 392 would be the better option. Dodge could probably go the supercharger route, blow the competition out of the water, but in the same manner, also move away from their long tradition of naturally aspirated engines. As far as a 426 or 440, Dodge already has the capability of the 512 V10 Drag pack.
Ugh, need a break.
In all, however, if the target market for Dodge is Camaro/Mustang sells, well, they look to get an engine that is comparatively close or better than the competition. Based on what Dodge has done so far, it seems like Dodge wants to keep their "muscle" engines naturally aspirated. So, the 426 seems like the viable option. Well, now we position the problem of getting it street legal, meeting fuel economy standards and thusforth.
So the 426....
HowStuffWorks "1964 Dodge 426 Hemi: A Profile of a Muscle Car"
There's the history, 1964 is the debut originally. So now lets look at this from a marketing perspective. 2014 is exactly the 50th anniversary of the legendary 426. It is possible that it can meet within the street legal standards. It'll probably have to be designed as such like the 392 to be somewhat fuel saver efficient. It maintains that it's naturally aspirated. It brings back the iconic legendary hemi that Mopar fans have known to love. It gets under the gun from the 2015 end cap of the federal government stepping in on American capitalism. So, by 2015, history repeats itself just like from 1970-75.
I am going to venture to say that 2014 is looking like a very good year to attend SEMA and see a "Legend" reborn. Worst case is that Dodge doesn't release a 426 from the factory and special edition the heck out of it. If so, then I'll just do my own 50th Anniversary special edition, all aluminum, 426.