The total volume of unconfirmed Txs may increase but I don't think so.

We got to about 2GBs of unconfirmed Txs in the last spike & it's back down to 1GB now. As fees unexpectedly increase, people add Txs to pull through stuck Txs. Some inefficiencies creep in.

I think in the next 10 years Bitcoins parabolic increase in purchasing power will drive the conservation of timechain space.