.... a team is progressing with its historical staff and a stable sprint length, and the time has come to assess the level of the team's commitment for the upcoming sprint.
It's human nature that individuals and teams with self-esteem set increasingly higher goals for themselves. By trying to achieve these goals, teams learn. Sometimes such strivings leads to immediate improvement, particularly when the team challenges itself to improve through use of a new-found technique or technology. Sometimes, however, the new technique doesn't pan out and the team's performance remains the same or even gets worse.
Sometimes, the team raises the bar just to raise the bar, either to test the limits or to unconsciously publish its bravado. Even these self-challenges can pay off, especially in the short term. It is more common that these higher levels are unsustainable in the long term.
Therefore: In most cases, the number of Estimation Points completed in the last Sprint is the most reliable predictor of how many Estimation Points will be completed in the next Sprint.
If the velocity actually goes up for a given sprint, consider Updated Velocity.