Who's gonna break this record?
I've seen many players getting 200+ scores. Strictly speaking, it is going to be more influenced by the situation.
I don't think Lara was thinking about 400 before going into the test. He got a 200, but it wasn't a good time to declare, so he went on, he got a triple and you might say it was the right time to declare. But also take into consideration how quickly he reached 400 from 300. He worked very hard for a triple so why not convert it to a quadruple.
He might just have thought that pressure might force a result in his team's favour, even if he played just a little longer. That was obviously a critical decision, but blaming him hard is just unfair. And, I certainly don't think an extra session would have meant victory for Windies.
Back to topic, only situations can make this happen. None knew Laxman is going to score 281, when his team was following on, neither anyone thought about Sehwag 309,... I won't discuss much about Sehwag, but the Laxman innings in my opinion was the best ever played by any player ever born. It was for the first time an extremely strong team leading by 274 runs and enforcing follow on, ended up losing. But had Laxman played a similar innings in 1st innings it won't have been respected to that extent and people would have been somewhat criticising a declaration at 657.
But, as we are talking about 400+, here are some possibililties
1. A weak opponent playing against a super strong one(e.g Ban vs Aus) and the stronger team batting 1st. A player can then get a 400+ score, but I can't deny it won't be anything very great whatsoever, although it will still take a lot of effort. Very respectable anyway, Players who may be able to do this are
Hayden (most likely), Sehwag, Smith, Gilchrist, Dravid, etc.(actually any good player)
2.A pressure situation, Likely players Laxman, Dravid, Kallis,(someone like Tugga)...
3.A situation even worse that Kolkatta, this one will be the best one.
Likely only VVS Laxman or a player like him.