When contracts expire you enter the status quo period you mentioned where both parties are expected to negotiate in good faith and maintain the majority of agreements. This usually does not apply to striking, of course, and you almost always need to strike to get a good contract.

To answer your question I think we'd have to be able to read your whole contract to be certain. Sometimes contracts contradict themselves, or at least seem to according to the lawyers both parties have to hire, so even if there's a line that says, "this applies until the contract expires" it may be contradicted by (1) the (enforced) law around status quo, (2) state law, or (3) other articles in the agreement.

Employers are not supposed to make any changes to working conditions during status quo, if that is helpful information. They are expected to bargain any changes and the union can usually file various legal complaints against the employer when they do inevitably change working conditions unilaterally. Though it should also be mentioned that the direct legal consequences are usually incredibly minor, so unions mostly use them as propaganda to make sure their members are pissed off and ready to strike.