Historically, not all Decembers have been bad for bitcoin, especially since we are in the middle of a bull run, there is no reason to be pessimistic that this month will be bad for bitcoin. Bitcoin also just crossed $100k and even touched $104k and this will be a historic milestone for bitcoin, so saying that December will be a bad month is completely wrong.
Altcoin season has started and will get crazier as we enter 2025 and I don't see any problem if people start moving to altcoins for better profit opportunities. But i wouldn't consider this diversification as the entire altcoins are still dependent on bitcoin. If bitcoin price corrects or suddenly drops, altcoins will also suffer the same fate, so it cannot be said that investing in altcoins is diversification to reduce risk.
I did not meant that this month will be so bad for BTC, as BTC just crossed $100k after I made this post, what I meant is it can make dip of %5 to %10 maybe in this month or even a small dip is enough to make market bleed and price of altcoins will also decrease and that can be a good time for all the investors to pick their coins.
$104k is really a historic milestone, and this is not the stop for BTC $150k is programmed, IMO. And altcoins pumping is dependent on BTC and if BTC drops alts will drop but if BTC will pump ALTs won't pump until it stabilizes itself, and sometimes BTC is dumping but alts are pumping that's when I think alts will be getting money from BTC.
To reduce risk we must diversify in high caps, like top 30 or max top 50.