No. Market categorisations change very rarely, and are determined by the number of suppliers that have their own equipment in the exchanges. (Except that Virgin Media cable also counts).
If there is just BT Wholesale and the ISPs that sell their WBC, then it is Market A. It needs there to be one of the ones on the samknows LLU list for the exchange for it to become Market B. If and when there is another Ofcom review. The last one was in 2014, the one before that 2010.
Changes in the suppliers between reviews don't alter the classification.
Few ISPs charge extra in Market A anyway. Plusnet did, possibly stiill do in some, and EE have or had an even stranger setup, where the exchanges that had Orange LLU are/were cheaper than all other exchanges.