Probably easiest to under with examples.
I'm assuming if you qualify for 2.6% rate you've a fairly substantial balance?
Scenario
1: rates stay exactly the same.
4 year rate is +0.222%. 2 year rate is -0.126
If you break in 2 years, fee will be balance * 0.347% * 2
The fee here will be marginally less than you'll have saved between 3% and 2.6%
Scenario 2: rates fall further. Say 2 year rate drops to minus 1.
Balance * 1.22% * 2
The break fee here will be more than you'll have saved between 3% and 2.6% (3 times in this scenario).
Scenario 3: rates rise. If the 2 year rate rises above 0.22%, there will be no break fee.