You can buy it, but without an LGA 1700 motherboard it's relatively pointless. The question of waiting always comes up, but at some point you have to have something new, no matter how much better things will be afterwards. You should always wait a bit for new chipsets until the drivers have stabilised, it's hard to say whether Intel/Microsoft will get it right from the start.

So it always pays to wait. The question is whether you can wait... unfortunately, no one can answer that.

Zen 3 with v-cache is coming in early 22, so are cheap ADL boards. I would wait.

According to rumors Intel 13th gen should came only at the end of 2022, roughly at the same time AMD Zen 4 will come. If you can wait for a year - I would wait, as it is expected their performance (both Intel and AMD) will be much better, plus DDR5 will be cheaper, motherboards will be cheaper and chip shortage may wear off.