To clarify: the limit you point to is the current throughput of tECDSA signatures per second that a subnet can produce (you need those in order to submit BTC transactions so of course the limit on those sort of implies a limit on the BTC transactions themselves).
AFAIK, the current implementation of tECDSA is not super optimized, so I would expect that this limit can be increased eventually. Likely there is going to be some limit on what a single subnet can do (the protocol is quite complex) but there is always the possibility to allow more subnets to sign using tECDSA which means we can “scale out” the throughput of these operations on the IC as whole.