Bitcoin being a bubble and/or crashing is a meme nowadays - and a very uninformed one, since it has crashed at least 4/5 times by now, and none of the crashes was permanent.
Everything has an end, but at this stage, there isn't any more indication that the end will be soon (or even not-so-soon).
I think the implication with many of the "it's just a bubble" comments is that "it's just a bubble [...and after it crashes it will fade into irrelevancy (eg. tulips or beanie babies)]". In that respect the prediction has yet come to fruition. However, if you're talking about it being a bubble in the same way that the stock market or the economy has bubbles[1] you wouldn't be wrong. The GP mentioned "Once it pops then the fun will be over", which makes me think he's closer to the first camp than the second camp.
[1] https://www.youtube.com/watch?v=XbZ8zDpX2Mg