21 out of the last 23 actually.
I don't think it will happen any time soon to be honest (after Fedal retire). Partially the reason is the ridiculous domination of Federer and Nadal on natural surfaces.
For example from 2005 RG to 2010 Wimbledon nobodyexcept Fed/Nadal won at those 2 slams. That's 50% of year's slams on lockdown by just 2 players.
Federer dominated hard courts, especially USO, with Nadal slowly improving there as well (2 HC slams in last 2 years, which is pretty good). So we are living in an era of 2 hugely dominant players, with others fighting for scraps, basically.
thanks for the correction, didn't want to dig deeper
But yeah, imo it's a predictable sport. It also takes an elaboration on defining "predictable", coz if we look the bigger picture, a dominatd by a couple of individuals sport is a predictable one.
Like F1 in the Schumi era or now the Rallies with Loeb.
But if we talk betting wise, it is just as any other sport - if you know it well, it's predictable, if not - it's not
If i have to state one unpredictable for me sport (nothing to do with tennis, so sorry for the off topic) it's the WTA