If past behavior is any indication the all star injury replacements in the East will likely be 2 of Porzingis, Butler, Young and White. Adam Silver usually picks players who finished next highest or closes to it in the fan/player/media voting. Those four were next highest overall in their positional groups.
My guess? Young and Porzingis.
Trae Young because he actually finished ahead of Maxey in the guard group but still didn't make it and has arguably been snubbed 3x in last 4 years. Porzingis because he's been better than Butler, played about the same minutes as him, and Celtics are #1 in East, and picking two guards to replace two forwards seems weird. Giving a second guy to the Heat who are around .500 would be strange.
Beyon those four I suppose you could argue for Barnes on Toronto, Siakam on Pacers, or Jarret Allen on the Cavs (he's been awesome since Garland/Mobley injuries). That's about it.