i dont think the Blu-Ray disc will hold 50gb of information. that is a little jumping ahead of the gun a bit.

I first read about Blu Ray discs 2 years ago and have been waiting to see them.
That article that i read stated that the discs would hold 26gb of data. This in itself is a ridiculously large amount of data.. i could back up almost my entire computer system drive on one disc.

As for the VHS / DVD thing.

i dont think the vhs has become a dinosaur. They are still more common than the DVD player in fact, and most people that have a DVD player also have a VHS.
Of course, like music cassettes, the VHS will be stopped in production, but i dont think this will be for a while.
a blank VHS is cheap and you can just stick it in and record something you might want to keep, and have a copy of it forever. i have done this with many music shows on television in the past.

You can record onto DVDs now, there is a DVD-Recorder that works exactly the same as a VHS recorder.
You put the disc in and you can videoplus programmes etc. these discs hold 3 hours, the same as a VHS, however the quality will be significantly better, and you get a main menu when loading the disc which allows you to name each programme you have recorded and then select them, like a chapter selection.
I dont know if they have got ReWritable recordable discs yet, but the Recorders themselves are about £300 at the present.
They will soon come down without a doubt, and obviously will be more convenient and save space to store discs than a load of VHS.
However i wont give up on VHS as it is very simple to use