Realistically?

Transformers/Power Rangers/Super Sentai cannot happen because of very obvious reasons (TakaraTomy vs. Toei/Bandai, Hasbro vs. Saban/Toei) ... someone has to "win" and neither side wants their property to "lose" so to speak because of the fact that they compete for the very same demographic in terms of boys action figure sales and, to an extent, television ratings (which mean nothing, it's all a vice to sell toys).

The only reason Avengers/Transformers happened in comic form was due to the fact that Marvel and Hasbro signed an agreement for Hasbro to do design and distribution for the action figure portion of the license (used to be ToyBiz). Now that Marvel is owned by Disney I don't know how long that agreement will stay in tact as Disney has always had their properties represented by Mattel, which would be awkward as Mattel handles DC's answer to Marvel Legends, and thus two distinct different license holders would compete against each other with the same company designing and distributing them.

...

Tangent, sorry.

It would be fun ... and maybe someday, long down the road, but not anytime soon.

Though if TakaraTomy ever successfully creates their own style of Tokusatsu, it could happen ... but that's not an easy market to get in to.

They can always unite to fight against a common enemy, like the Super Hero Taisen!

Also, look at EVERY Sentai Vs.
They're always a team up :p

Tamashii's right, Kicker. They start off fighting each other because they were both lied to, and then they join forces for some heavy metal kickass.

This thread makes me really curious as to how many members on Tokunation are from TFW2005.