When the "See You At The Next Gundam Fight" thing was inserted, no sequel was planned. It's part of the director's personal style-- he doesn't end his shows conclusively, but instead does open endings which hint at future adventures the characters might have.
Apparently G Gundam was so popular at the time that Sunrise actually did pre-production on a sequel before the project got quashed by (so I hear) the Gundam Group, which didn't want to dignify any of the 90s alts by letting them develop their own extended universes.
Apparently Gundam Wing turned into a battleground over this issue, because the fan appetite for sequels and spinoffs was clearly there. I've heard that Wing's supporters in the Gundam Group had to fight really hard to get Endless Waltz made.
Anyway, I posted about this in the 00 movie thread, but: the going rumor about the next Gundam series is that something will be announced in March and airing will begin in September. The rumor says that the next series will be a return to the UC timeline, but take this with a grain of salt-- I've seen that rumor before.