a heavy adoption of Tether for it to reach up BTC cap level.
Im not saying it isnt possible but would really need extreme level of adoption and recognition of tether,if not then it would just remain as it is when it comes to rankings.
It might being hyped but wont really be enough.
as long as "top spot" translates into "bigger market cap" or in most cases "bigger supply", i don't think it would be that hard for any shitcoin to go above bitcoin and become "top". all it takes is an enormous supply with only 1% circulating and a tiny price.
but if you change the meaning of "top" to mean actually top considering value, adoption, utility, decentralization, security, price,... then non only it becomes impossible for them to be the "top coin" it also becomes impossible to even have 1/100 of bitcoin's rank.
The coins in coinmarketcap are ranked in order of their market capitalization which is price*circulating supply. So, it's not easy for any coin to be higher than bitcoin only with having a big supply.
What matters is their circulating supply not their total supply.