There's still a lot of games left so it's true what you say anything is possible including Newcastle not being in the top four, but the advantage that Newcastle has is that they have no other competition besides the Premier League so they can really focus on one goal which is to get spot in the UCL next season, different from other competitors who still have to compete in other tournaments
Moreover, this advantage of concentrating on one tournament this season is much stronger than in any other. Due to the World Cup, the calendar of games is very compacted and teams that play in several tournaments will suffer greatly compared to those who play in one. I think that the difference will be felt by the end of the season more and more, and even some top clubs will fall into failures.
Considering that this is a competition once every four years, all players will definitely be risking anything and of course there are many injured players after this world cup is over. Even those who did not take part in the championship are saddened by the injuries they received while playing in the league. I agree with you that there will be many top clubs who will fall after the world cup is over regardless of what will happen later, usually this happens because the performance of players is not as usual plus there will be many transfers of players next season which makes some teams stronger and this will change several teams' positions in the standings.