I don't think you need refi unless you want to cash-out

1)You still have 5 years ARM.

2)Your loan amount is small. But your refi cost percentage is high(at least $3000 to $6000 depends on the rate, so at least 3% of your loan amount).

3)If your ARM cap is 2%, you will have 6th year rate low.

4)6th year later, the your loan amount is less than 100k. Your risk is minimum.

You can refi if you want to use the extra equity to invest.