> Could the second one mean "I will (IN THE FUTURE) ride the train everyday"?
Yes. For example, if the person who said this sentence lives in a small island now, it surely means "I will ...".
> And is there an adverb to make it more obvious to mean that?
As you probably know, there is no "simple future tense" in Japanese, but there are many ways to describe a future plan/volition. Examples:
* ****
* ****
* ****
* ****
* ****
* **** ( = from now on)