Ok, so the 4 biggest competitors are Max, Matty, Ruihang, and Tymon.
According to SpeedcubeDB,
Average TPS:
Max-10.8
Ruihang-10.8
Matty-10.3
Tymon-9.5
Average Movecount:
Tymon-53.5
Matty-55.4
Max-58.7
Ruihang-59.1
Global Average:
Tymon's Average-5.65
Max's Average-5.44
Matty's Average-5.38

Ruihang's Average-5.48
So, Matty should be most likely, because he has a lower global than Max, Tymon, and Ruihang.
But we haven't factored in Comp Nerves yet.
Comp averages are obviously a lot different than averages at home.
Comp Average from the last 3 Months :
Tymon-5.84
Max-5.70
Matty-6.00
Ruihang-N/A
So, according to Comp Averages, Max should be the first to get a sub-5 average. But that's not fair either, because Ruihang hasn't competed for a year.
There isn't really an easy way to calculate this. Matty has one Sub-5 fail. His 5.25 Official average would have been 4.93 without the +2.
Tymon also has a Sub-5 fail. His 5.15 average would have been 4.74 without the +2.
Max and Ruihang both have no Sub-5 fails.
If you have watches Matty's 5.25 video, you will see how many lock-ups he has. Without them, the average might have been WR and Sub-5 even with the +2. If Matty can fix his turning, I think he will have Sub-5 average in the bag. So overall, I say Matty.