Green Gibbon! of the Neo Green Hill Zone is saying that “Samba” in the Sonic Team logos refers to an arcade game called “Samba de Amigo”:
The Team’s first crack at a coin-op, Samba de Amigo challenges players to grab a pair of maracas and shake along with progressively difficult beats. The player shakes the maracas in accord with the six indicators on-screen. The quality of your performance is graded on a letter scale (so it is a Sonic Team game), and two players can rock & rattle at once.
We don’t know if this will be released Stateside, or even on the Japanese Dreamcast. But, hey, Sony gave us Parappa the Rapper, and look what happened.
GG!, DCHQ, and Dreamcast Magazine #1 are speculating that the “Pso” logo refers to Phantasy Star Online. If this is true, we’ll have to wait a while until we get NiGHTS 2. But stay tuned, because anything can change.