[A_D_E_P_T]

> I believe proton decay is still considered hypothetical

Definitely.

> [link] is a good overview

That overview seems to overstate the likelihood of proton decay. In fact, it has it backwards. The default position is that protons are stable, per the standard model, not that they're susceptible to decay.

[jessriedel]

> The default position is that protons are stable, per the standard model, not that they're susceptible to decay.

It's only the "default" in the sense that the simplest model explaining data gathered to date (the standard model) predicts no decay. However, most physicist do not believe the standard model is the last word (and surely it cannot be when you go to the Planck scale), and many models post-SM models predict proton decay. I would guess if you surveyed high energy physicists, you'd find the majority expect the proton does in fact decay, so it's the "default" in that sense.

[A_D_E_P_T]

Apologies for the late reply -- I just saw your comment now.

I don't think it's the case that many post-SM models predict proton decay. A few do, but even those are now tightly constrained by observations that place the proton's half life at more than 10^34 years. A lot of models that previously predicted proton decay have been empirically falsified on such grounds, and those that remain are looking pretty shaky. So I don't know. If you run that survey, I believe that the average physicist would come out against proton decay. It would be an interesting survey, in any case!!