Learn Dutch: De rest komt morgen. - The rest is coming tomorrow.

In Dutch, you can often use the present tense to talk about the future. Because the sentence includes the time word morgen (tomorrow), it is already clear that this will happen in the future, so you don't need to use a future tense verb like 'will'.

If 'the rest' refers to a group of people or multiple things, shouldn't the verb be plural (komen)?

No, de rest is strictly a singular noun in Dutch. No matter how many people or things it refers to, it always takes a singular verb like komt.

I learned that morgen means 'morning'. Why does it mean 'tomorrow' here?

The word morgen translates to both 'morning' and 'tomorrow'. You have to use the context to tell them apart. Here, 'The rest comes morning' doesn't make sense, so it must mean 'tomorrow'. If you specifically wanted to say 'in the morning', you would usually use in de morgen or 's morgens.

How would the sentence change if I wanted to emphasize 'tomorrow' by putting it at the beginning?

If you start the sentence with Morgen, the verb must stay in the second position. This means the subject (de rest) and the verb (komt) have to swap places. The sentence would become: Morgen komt de rest.