Well, it seems it may well have been in production for the old breadbin, even after the mess of the first game.
Issue #59 of Zzap 64 announced that Activision had gained the licence for R-Type 2, and work was to be started soon. Zzap followed this up almost a year later in their Christmas Special (#68) that the game was being converted along with another game called Beastbusters.
But sadly this is all we ever heard about the game, and the idea of a C64 conversion faded into obscurity.
Rumours are that Arc Developments could have played a role in the C64 conversion, though after previous contact with Richard Underhill, he never mentioned it. We will ask him again with regards to the C64 conversion, just incase.
It is possible that Activision decided to ignore a C64 conversion, as they started to move away from the C64 around that time. I think the last lot of games from Activision were Sonic Boom and Galaxy Force 2, both from around 1990 I think.
A lot more research needed to find out if anything ever was started, and if the plan was true. The magazines reported it, so who knows?
Did it ever exist?…