Bitcoin has a problem in his future - its not a green currency at all, it consumes too much energy and computing sources, there is a good gap for all PoI networks. The success of PoI based transaction network is determined by 3 things:
1) stability
2) publicity
3) sustainability
If all 3 points will be valid, there will be no reason to replace PoI in future (and there will be enough hope that PoI will be the "last" step for many years solving all imperfections of BTC PoW concept). BTC (with its old PoW concept generally) is so much successfull because it is (almost technically) stable, has a good publicity and was sustainable (and will be until it will become unpopular due to big energy and resource demand - it consumes really horrible amount of energy and production resources).
There is no reason to think about bitcoin demission and it wouldnt bring anything positive for market in general. Its comparable to MMORPG games, old concept may coexist with new concepts and be relativelly independent, however only new concept will grow up, the old one will stagnate and being slowly demised for many years (look at world of warcraft as an old obsolete concept vs. new 3D action MMORPG simulators like world of tanks or war thunder). Now compare it with crypto.
WoW = BTC, first concept, had many epigons (crypto: all PoW shitcoins and "altcoins"), many of them got some community and survived but never succeeded because they have brought nothing really new or innovative.
WoT, WT = 2nd generation crypto. Projects with good innovation based on another game engine (in crypto another crypto algoritm and transaction network), another community, absolutelly different mechanics etc. and they are absolutelly independent on other projects. There is a big competition between WT and WoT (same like there is a competition between PoS currencies) because they are similar in its own generation and used by similar community.
The only question is how will be NEM going in future. Concept is good, idea excellent, question is what about the people behind it and technical backup. The crypto in general is fragmented into many projects which go nowhere or just have no credibility. This may be also good for PoI / NEM because there is a big hole waiting for anything what will fill it up.
What i really miss for now is a propagation which /my 2cent/ is a bit underestimated and below expectations adequate to initial distribution and development. Sometimes is being a little quiet more healthy and better than loudly empty promises and PnD which we know from other projects and "projects", however there are some questions which need to be solved faster than it happened. E. G. the trademark or logo - without this i cant e. g. wear a T-Shirt with NEM logo because it may be changed again. Thats are the small details which may lose the war...
WoW and Wot, WT are all the same things, i.e., about games.
PoI is only an incidental, but important component of NEM. NEM is
NOT ONLY just a coin. Being a coin is only good for what it is. NEM is a platform, an ecosystem that survives on its own economy. As an example, one can make use of the NEM infrastructure to issue their own coins for their own uses. If you are some games developer you may want to have a special token for your game and you may not want to build your own altcoin which is not your focus. You can then make use of NEM's platform to issue your own coins. Leave the rest of the harvesting (mining) to the NEM community to manage that for you.
Consequently, your community of game players can then propagate it among themselves. There is also a possibility that your coin has some value and therefore can be traded with other game coins or altcoins or even exchange for real money in an exchange (e.g., using AltNemo's FTE).
Logo has already been decided. Trademark is not part of a decentralized movement, I am afraid. The word protectionism does not exist in a crypto initiative unless it is a private entity (which is a centralized entity).
Nxt and NEM are in a different league compared with all the other altcoins, including Bitcoins. Some of them are niche while some of them have their own purpose. But if there is no ecosystem on a coin's use, it will not survive long.