Mario is simply one of the best heroes all year round as he is the one that the Mushroom people can depend upon all year round. He would help them as long as he can, but no one is sure till when that would be since Mario is getting old. People are getting old and certainly Mario isn't free from aging. At some point, he would get replace, but till then, he would still be the hero that brought Mushroom kingdom to its greatness. At least, with King Kuppa not around the people can concentrate on their own living.
Overtime, A new threat arises and Mario need to defeat the new threat. But, that won't happen till he finds out what is the new threat is all about. He need to investigate what is causing some of the dangerous creatures go amok. One thing is certain, this guy wold be strong to cause all that trouble and that he can't be defeated easily. Fortunately, there are things in the castle that he can use against the new guy and it would help him to get the advantage. When he found out, who the new guy is, then the fight begins. but the danger is not all about the new guy as the castle is beaming with lots of danger.
In this game, you would need to explore the area. There are coins almost everywhere and you need to collect them since you would earn a life at one point when you have collected enough. The place is filled with danger; traps are almost everywhere and you can bet on it that there would be some minions roaming around the area most of the time. You can't fight them if you don't have some powers, so it would be wise to avoid them. At least, till you have the power to fight them, otherwise you would just die.