As far as I know (but I don't own any Android device, only iOS...
), MIDI lyrics display is currently not supported in Winamp for Android, but it could be in future versions I think...
(Correct me if I am wrong).
If you want Karaoke Lyrics on a tablet, consider buying an iPad (you won't have Winamp though). But there are many very good apps that playback MIDI with very high quality (included 100MB of soundfonts) and also display the MIDI lyrics. One example (my favorite one) is "modizer" which, as the name suggests, also plays all kinds of MOD/XM/etc. files in fine quality. It's USD 1,99 and totally worth it, I think.
Maybe it will be available for Android some time, but I don't know. For Android, there is Droidsound for playing MODs, but I don't know whether it can display lyrics or if it can even play MIDI at all.
Hope I could help...