I was complaining about this since March at Toyfair, and even to Hasbro at BotCon (saying that it was a wasted opportunity not reissuing the Crossovers toys, that already exist, for the Avengers Movie)... and it seems someone at Hasbro did have the same idea. It's just that no one from the Transformers Division knew about it (Marvel and Star Wars Crossovers are not done by the Transformers Division).
And it is still a bit late, as the Movie was out last month here, and 2 weeks ago in America... and these toys were only just found on ebay, so could still be another month away from release. (not likely to be here though)


They're now called "Transformers Mech Machines", and are given some new vehicle names.

There are three shown here, but there may be more... as Hasbro did a Hulk toy as well (which isn't shown).

Captain America/Assault Cruiser - appears unchanged from original version.

Ironman/Arc racer (a concept name from the movies) - has gold colouring instead of yellow, and a blue chest.

Thor/Thunder Bomber - all yellow parts are now black (legs/engines, hammer handle, waist, jaw)


UPDATE -
I just read through the comments on the news topic linked above, and found that these were announced in a press-release at around Toyfair earlier this year. Two of them were (Ironman/car and Hulk/tank), which means all four are being released.

MARVEL THE AVENGERS MECH MACHINES Assortment
(Approximate Retail Price: $17.99; Ages: 5 & up; Available: Fall 2012)
It’s definitely MORE THAN MEETS THE EYE when these AVENGERS ASSEMBLE! Each detailed robot toy is modeled after one of MARVEL’s AVENGERS super heroes, and converts to a vehicle form! Choose from IRON MAN/SPORTS CAR and HULK/TANK! Each sold separately.
Looks like the US Retail price of these have gone up $3 since they were last in stores.