Well if you are waiting for the 2s to come back, that is never going to be a thing again in your lifetime. With this being a election year, I suspect rates will improve. But somewhere in the 5s is probably the best you are going to do for a long time.
Now what you could do, is put extra money into paying off your current house faster. Then make it a rental, and then use the rental cash flow with your existing cash flow, to then buy the much bigger house.
But I feel your pain, because I will never give up my 2.5 percent rate. I am staying in this house at that rate, till I retire....it is just to sweet a deal.