If you have a gambling mindset, then you can try alts.
Let's not pretend that BTC's price is necessarily strong and stable. It's always had very drastic fluctuations. Even though that doesn't have to continue forever, it's very likely that this drastic increase will involve another drastic fall at some point.
wait for another Dip
I'm already into Bitcoin from before this whole bubble situation started, and I'm not going to be buying any more in the near future. I'd rather buy in a full-on bear market after it's been going down for at least a few months, rather than just buying in as soon as it drops a tiny bit.
Especially since I'm already holding BTC and it's a pretty risky asset in the first place, I'd rather not gather any more in an even riskier time.