With BTC close to 30k, investors are looking into a potential 5x from here going into the next cycle. This is where the multiples on altcoins become attractive.

At 30K and beyond BTC will be keep being pumped mostly by institutional money flowing in. Those are veteran investors and they prefer the proven track record of bitcoin as a hedge for their money against the growing inflation of the dollar.  

Mid-scale investors will look for other projects that outlived the 2018-2020 bear market and still have active development, good technology that will shape the future. Those projects are still ways away from ATHs and can probably see a 100x (maybe)

Crypto veterans same thing. They are risk takers. A lot is still on the sidelines in tether(20B) or other stable coins and i would bet that a large chunk of this will be going into solid altcoins instead of BTC.

Also with the whole XRP fiasco this brings fears to Tether(USDT) being targeted as well. Although this may seem scary it's actually very bullish. XRP was a top 3 coin, so is Tether now. Those billions of dollars are not exiting the market by any means, instead they are flowing into solid projects.

Some of those projects that are highly likely to achieve enormous gains over 2021 are Cardano and Vechain. And a few others most notably Polkadot will grow a lot as well.

There will also be great gains in the DEFI space but that includes considerably higher risk and will most likely be ignored initially by retail since money flowing in this bullrun feels like smart money and it is only going into solid projects and we are not seeing those gains across the board like in 2017.