A company does not cease to exist simply because it goes bankrupt. The company may wind down its operations, but it may just go through a process of restructuring its debts.
If the company is merely restructuring, the bankruptcy would not probably not have much effect on its ownership of intellectual property such as copyright and trademark rights. So it would retain those interests in the video game, and the sequel company making the sequel would need to obtain licenses from the original company.
If the original company is going through bankruptcy in anticipation of shutting down completely, you can expect it to sell off all its assets, which would include its copyright and trademark interests in the game. In that case, the company making the sequel could either attempt to purchase those rights itself, or it would need to obtain a license from whoever does buy those rights.
