Nothing yet.

Mentioned at the end of the first game, Tiger Road 2 was of course the sequel to the not too bad Capcom game. The C64 conversion of the original was good for rose tinted reasons - comparing against the arcade, its completely different in places and quite boring.

You'd think that the C64 developers would be referring to a potential conversion of an existing conversion, but research didn't find any sequels - so was it a bit of tongue in cheek?

We believe that this is vapourware, but can anyone confirm? ...

Were US Gold to do an unofficial sequel of their own?

Frank.
(Additional source credits - C64 endings)