Arena points

Okay, whats cap on arena points we can have, AND are arena points gonna flush at beggining of new season?

Arena points should be reset for all characters when a new season begins, yes.
As for the cap I can't remember exactly, I think 5k ? Confirmation needed.

No, you could save up to 5k points until the new season. This isn't WotLK.
5k is the cap.