A last minute confirmation that Season 5 will be ending today, April 14th. This coincides with the release of v3.1.
Arena points are not being reset tomorrow. They will be reset with the beginning of season 6, which could come as early as April 21.
Original Post: 3/31/09
Word from Blizzard: Arena Season 5 will be ending in 2 to 3 weeks.
The following Arena Season will not begin for at least one week after the current season ends. During this time between seasons, all rated matches will be turned off and only skirmishes will be available. When Arena Season 6 begins, all teams, personal rating, and arena points will be wiped, but matchmaking rating and honor points will remain.
Don't forget to check out the title calculator to help you out as you push for gladiator this season! Have fun.
Special thanks to vexo and Zamboni for bringing this to our attention so quickly.