I think this is very unlikely.
Maybe regionalism in a form of free-trade agreements, closer
ASEAN integration, etc, that is still possible, and I believe this
is the trend that is going to take place in the future, not just
among Singapore-Malaysia but more.
But to be one country, I dont think so.
The reason is the population.
If we look at history, only countries which share similar
demographics will willingly merge, for instance West Germany-East
Germany, or even Bellarusia-Russia which form a kind of Union,
because they share a common affinity or common identity towards
each other.
If we look at Singapore and Malaysia, it cannot be argued that
the demographic is similar.
For this reason alone, no merging will ever be possible.
Meat Pao