A product upgrade normally does, unless a special arrangement is made.
A new contract wouldn't be too bad if one just monitored the line for a few a months on the 40/20 product, then, if performance justified it, an upgrade might be feasible.
How could the line be monitored: I guess checking the BT profile after any re-syncs might give an indication of any degrading performance if the modem stats are inaccessible?