I doubt it because the efficiency takes more thinking and more planning, which they do not do too much of. I don't think Yiheng Wang, Ruihang Xu, or Yezhen Han don't even do COLL. If they somehow figure out a way to combine those then sub-4.5 is definitely possible but I don't think they will get under that with just their tps. 60 moves/12tps = 5 seconds, but 48/12tps = 4 seconds, and I don't think they get sub-50 move solutions without a skip. On Ruihang's 2.68 he didn't stop to recognize the WV, which would have saved him 3 moves and most likely a sub-2.6. It is little things like that which will hold them back. Not saying they aren't rapid, but they probably won't be too efficient in the near future in my opinion.