New Sonic the Hedgehog games are arriving (seemingly worldwide) in the Summer, but Japanese fans are the first to know when exactly those games will drop. Sonic Adventure DX on Gamecube will hit stores in June 2003, with the GBA's Sonic Pinball Party arriving the month after.
Specifically, the Sonic Adventure port will be available from June 19th and will retail for ¥6,800. Sonic Pinball Party will come afterwards on July 17th, and sell for ¥4,800.
No specific release dates have been announced by SEGA for the UK and US, but we know that we will also get them in the Summer, so no doubt they'll be available at around the same time.