This is probably incorrect. The 5.0 is already a bored out 4.6. I'm pretty sure you can't bore out a 4.6 to a 5.5 without having major issues - at least from a production car standpoint. If they really wanted to increase the HP that much, they would probably move back down to a 4.0L twin turbo v8 - similiar to what is offered in the BMW 550.
That being said, if I were a gambling man I would bet on the 5.0 staying around in the rspec for at least the next 2-3 years.
Much of the 4.6 and 5.0 is a copy of Ford's modular design. That includes the block and crank set up. In fact, it can be increased (bore and stroke) to 6.2+L. As Ford has already done and in production. The TAU platform because of its basic copy design of the Ford modular system has much potential improvements.
One of the reasons why Ford has kept FI instead of DI for the V8, is the issue with intake valve buildup. The heads and block as Ford indicates is "DI" ready. They have been testing dual FI/DI and DI designs.
Because of the basic tooling and design, like Ford, it will be easier to improve the block, heads and intake design also.
It is not "chance" that Hyundai chose the exact displacement of the Ford V8 designs. Ford uses a 3 valve head currently (back in mid 2000s used the 4 valve seen in Hyundai) except for the GT500 which is 4 valve.
And my 5.0 sounds like my 4V Mustangs less a supercharger and a quiet intake and exhausts. Like a more quiet, yet deeper sounding my Marauder (which is 4 valve but 4.6L).
The Hyundai engine is amazing. Such refinement, performance and MPG.
Point is, with little or no
mods, they could go to at least 5.4-5 (just like Ford) and likely go to 6.2L with small design changes modular system (again, just like Ford). Imagine a tweaked Raptor engine in the Genny... Now there is a CTS killer. Or a 5.4 supercharged, which at 650hp, would slaughter the rest.
Ford missed out by canceling their RWD mid sized new program 5 years ago. Imagine GT500, Boss 302, and Raptor like engine options... Coupled with the chassis design they had ( and Mazda had access to, and Hyundai also got their hands Mazda's files for research on the Genny), Ford/
Lincoln would have had a global sedan killer.