I'm considering buying this tuner card:
The list shows it working with many Hauppage cards, but the WinTV Go is not listed. Can I use GB-PVR with it? If so, which option would I choose?
No, this card will not work with GB-PVR. You should get a Hauppauge PVR150 or PVR250 instead.
Will it ever?
The others are way too expensive for me and nor do I need anything fancier than this.
How about the ATI Rage 128 Pro video card. It's a 32MB AGP video card with composite input. If not, will it ever?
No sorry, neither of these will be supported.
GB-PVR is designed to work with cards that contain hardware MPEG-2 encoders like the Hauppauge PVR150 or PVR250 etc. Both of the cards you mention are software encoders, and as such will not work with GB-PVR.
A PVR-150 can be had for about $69, so they're not really expensive.