Threats are the tactics of the powerless.
As Yoda said, do or do not. There is no "try".
So the Johor prince has articulated Johor's perceived option to secede.
Lawyers say the Constitution is silent on secession.
Just as it was when Singapore left the Federation. It took passage of a bill in the Malaysian Parliament to allow Singapore to leave the Federation. Thus it is not the unilateral decision of Johor to simply secede.
I do not think it is possible without a war of secession, and I do not believe such a war is likely. It is to nobody's benefit for such a war.
So it is simply posturing and threats, at this point.
Of course, it got Singaporeans excited. Some Singaporeans.
Who saw opportunities instead of threats.
Sure, there are some possible opportunities. Johor may decide to re-negotiate a new water agreement - one that outsource most or a significant portion of their water needs. But this is by no means a sure thing. It depends how much of the Malaysia Boleh pride is translated into Johor Boleh!
Certainly seceding from the Federation would whip up Johor pride. But the water re-negotiation need not happen immediately.
Others see the possibility of a closer working relationship between Johor and SG - in terms of transport, housing, employment, business. workers can cross the border freely for work, play, and even housing. Businesses in SG will have a larger domestic market. SG will have the "hinterland" we always wanted.
Some go as far as to wonder if Johor and SG could merge as a new state.
There are too many differences - politics, ethnicity, political philosophy, economic development stages, etc.
But it was nice to dream for a while. As long as we keep in mind that it is simply unrealistic dreams.