For a worldwide tsunami to happen something big would have to happen, the most likely possibility is a direct asteroid collision with Earth. Now as far as i am aware there is the apophis asteroid which is supposed to pass Earth in the year 2029 and the threat of a possible direct collision in 2036. A worldwide tsunami will not cause the world to end as such but it will cause massive depopulation of Earth in both human, animal and plant kingdom.
Everyone always says "he didn't say he wouldn't destroy the earth by fire." when people ask about flooding. He also didn't mention cheese whiz. It's a ludicrous argument meant to scare people into believing in boo-scary deities out to smack them if they don't believe. Climate change may cause waters to rise in general as the ice melts, but this is not a tsunami, which is a tidal event caused by tectonic activity. Earthquakes at the floor of the ocean cause tsunamis but even here, those will only be a danger to coastal areas.
Not only that, but a great portion of the world canNOT has tsunamis:
Central United state and canada
Russia and Western China
These locations re just plain too far from the ocean, and to high in altitude, to be affected by a tsunami. There simply isn't enough water in the oceans to do it.
god said he would not destroy the earth by WATER, be He said nothing about fire! The Book of revelation gives very string hints that a rogue asteroid will at least be involved in the end of the world (Look up "Wormwood"), and other locations give evidence of a fire 'so hot the even the elements are destroyed". The ONLY possible way this could happens is an exploding sun. Man does NOT have enough nuclear capability to destroy the earth -- we can only strip it of most life, the but the EARTH would still be there.