T5 isn't going to be the new standard.
One reason playtest was so open was because you are wrong in at least one sense.
Traveller5 is intended to be one sort of "standard": it's Marc's view of how Traveller works. This creates a ripple effect. When it makes statements on how particular in-game effects work, such as
how jump works, it is intended to either restate, augment, complement, or replace previous statements as a successor to GDW Traveller rulesets.
This also spills over to Traveller books published in the future, regardless of publisher. Marc can simply point to his core rules when a publisher wants to know how something works. Similarly, a publisher could potentially refer to the T5 Core Book to handle explanations, freeing up room for his own content. Or (better), Marc can derive a reference supplement from the T5 Core for that purpose.
Fanbase Fragmentation
One concern is that Traveller5 may
fragment the player base more by adding yet-one-more rule system in a Babel of rules systems. I think that people who like Book 2, High Guard, MegaTraveller, TNE (and so on) will continue to like the product, but what I think will happen is that Traveller5 assumptions will begin to take priority, with other systems having vocal minority inputs.
In the best of all possible worlds, those minority inputs will influence Traveller5 (after all, BCS is yet to be published, and Traveller has no Operational Warfare rules, yet).
Subsystem Adoption
As far as the subsystems go, people are free to pick and choose the bits they like and ignore the bits they don't like, and I think that can only benefit Traveller in general. But some referees will like the synergy between Traveller5's systems, and prefer to use it wholesale, rather than taking only one or two subsystems and grafting them into another rulesystem.