With 50% of the hashrate you're not Selfish Mining anymore; you're effectively able to take over the network since you now can outrun the other miners indefinitely.
I totally agree and that's why this kind of attack is not really a viable threat, because if you need 50% hashrate you can do whatever you like.I found this realistic model of selfish mining (as opposed to hypothetical theoretical models):
Source: https://medium.com/@ProfFaustus/the-caner-that-is-the-selfish-mining-fallacy-ed65c20a6ce7
where we can see that the selfish miner revenue (orange line) surpasses the honest miner (blue line) revenue very close to 50 percent hashrate.
If that's so, no point even discussing this kind of attack.
Thank you! This looks correct to me, well put and nice plot.
Also see: http://vixra.org/abs/1504.0072