There are two counterpoints that mean that this is unlikely to be what happens:

Lego bricks are made to micron tolerances. When you add up tolerancing errors over 10 or 50 bricks in a row the differences can add up and things don't fit. This is a big part of how Lego saw off the cheap competition - they were generally not satisfying to build. This is achieved with very careful injection moulding, and the only rapid prototyping tool at that level of precision is 3D CNC.

There is more to the sets that pieces of plastic. Look at Warhammer - the figures are all plastic, they could easily be 3D printer, they might not look quite as good but they'd work just fine. Yet, Games Workshop sells set after set. Lego sets are also designed, come with instructions etc. There's more than just the components.

A friend prints lego rail tracks that don't exist but should.

For regular bricks, however, Lego's manufacturing process is incredibly precise in a way that I don't think 3D printing will ever be.

You can make Duplo blocks. I printed some nice adapters that let you build a bridge for wooden Brio railroad tracks, with Duplo stands. And it think you could make specialty parts, like it excavator arms. But for regular Lego pieces, printing is too expensive and not accurate enough (don't know about resin, but I can imagine it is not flexible enough or too toxic?).

What's really holding us back is copyright. I wish there were high quality Ninjago or especially Star Wars clones.

There is no problem buying the parts separately needed to build such model. Of course, some exotic parts were discontinued. Lego provides instruction as pdf on their website.

Edit: the other brick manufacturers have problems replicating brick quality with injection molding machines. I assembled thousands Lego parts with my son and their fit was exactly the same - perfect. The Chinese kits have one in hundred parts that doesn’t fit well. However it was one in ten some years ago, Chinese learn fast.

I doubt one can 3D print anything as Lego replacement.

Competitor brick quality is on par or better than Lego at least for some. You need to do a little research on which competitors use which brick producer, but for example the bricks I’ve had in the Mould King sets were absolutely indistinguishable from Lego bricks in quality.

Building Mould King right now. The difference is almost gone. Cada is worse than Mould King. Anyway with 5x price difference I can live with a bit lower quality. Lego pricing is just sick. Even used sets from not that distant past.

They have much much better quality, but the resin is usually brittle compared with ABS.

Also it releases fumes that are extremely bad for children. There are quality resins but costing $100 per litter or so.

Today with 3d printers you just can print connectors and connect aluminum beams and wood boards to do whatever you want.

I teach children to cut wood boards with a fret saw and to mark holes that we drill super fast with a column drill machine.

They also know how to create basic shapes with the FDM machine, and print standard connector sets.

They have today way more advanced options that Legos.

The tolerance to which Lego bricks are fabricated is impossible to achieve using affordable gear.

It’d cost more money and time to print inferior parts.