2021-2022 projected roster
Murray
White
Lonnie
Tre
Vassell
Luka
Eubanks
Dieng
Poeltl
2021 FRP
Keldon
KBD
That's 12 players (assumes Dieng is re-signed and KBD comes back on a real contract as opposed to a 2-way)
2022-2023 projected roster
Murray
White
Lonnie
Tre
Vassell
Luka
Eubanks
Dieng
Poeltl
2021 FRP
Keldon
KBD
2022 FRP
That's 13 players (assumes Lonnie is re-signed)
Then in 2022-2023, add the first round pick that year and it becomes 14 players.
The roster seems full in a few years to the point where the team would not be able to draft a player and have room for them, so perhaps we could see a small shake-up. It's also possible KBD doesn't stick, and one or both of Luka & Lonnie are let go. That would then give way for roster flexibility (but for what? The Spurs aren't expected to sign big fish in regular years). The Spurs' view of Luka is such an enigma and this off-season should reveal everything about how they feel. As for Lonnie, I'm starting to feel his late season surge and the bonding with his teammates indicates he's here for the long-term.
By the way the roster is becoming full, I could see the Spurs giving up a future draft pick + DeMar this season for a bigger fish. Maybe a player from another team becomes disgruntled.