Dell E Series lifecycle + docking stations

Our laptop assets consist of Dell E series laptops. Most laptops (approx 50) have the standard dell docking port station.

As Dell change the design with each revision including the dock port style and position, does anyone know if Dell are introducing a new series anytime soon or in the near future? I don't want to have to spend £200 on a dock only for the next laptop not to fit.

Of course there are the USB style docks which will work on any laptop, obvious downsides is to keep having to plug the AC charger in.

How do you guys manage this in your organisations, 50 x £200 is a lot of money to spend every 5 years or so adding in the price of new laptops, screens and stands.