Yes, the trains are indeed secondhand. If you look at the quote from the SNCF, with the benefit of this knowledge, you will see they do not actually say the trains are new, they only speak about the interiors !

The trains now starting use on the TGV-Est were built in the early 1990s for the TGV-Reseau service. They have been refitted inside as you need to do with trains (and indeed planes) after about 15 years service, and Christian Lacroix has done the design, including the asymmetrically-shaped seats with slanted tops, mostly of one colour but with odd ones up and down the car in a different colour (standard class are purple with odd red seats, first class are blue with odd green seats. Only in France.... ).

These trains are being replaced on the TGV-Reseau routes (the non-Paris routes, eg Lyon-Lille), which cross France elsewhere by new Reseau-Duplex trains, Duplex being the French expression for double-decker.

The maximum speed is more a function of how the tracks have been laid out (eg minimum curve radius) rather then the vehicles themselves, and how much electricity you find it economical to consume.. TGVs on test runs on straight sections have gone very much faster than this maximum.

On the new TGV-Est there will also by German ICE high speed trains running, and similarly the French trains will run on into Germany. The arrangement is that the French will operate the Paris-Strasbourg-Munich route while the Germans will operate the Paris-Saarbrucken-Frankfurt line, not passing through Strasbourg.