I have a feeling that SEGA wasn't planning for a Dreamcast collection at first. I think they had SA1 planned for last year, then when Crazy Taxi was decided upon they probably chose to delay SA1 until CT was ready. At that point they probably thought: "Hey, let's just release these around the same date (9-9-10, my guess) and say they're the first of a Dreamcast rerelease collection."
I'll bet that at this point they're picking more Dreamcast games, hopefully ones that aren't PC or Gamecube ports, and we can probably expect better emulated games in future releases. Or at the very least, games that are direct versions of their Dreamcast release and not some PC/GC/PS2 hybrid.