Is it really the same ride anymore if they completely replace the track? It feels like what you want is a brand new ride with pre-2000 theming, which isn't particularly realistic. The original X was a product of its time and doesn't really have the same mystery in today's high tech environment. Getting a full loop + track inside the pyramid would also be a serious engineering challenge, and utilising it would probably require a powered launch, which again completely changes the ride experience.
That's why it makes more sense to just tear it down and start again. The space could be much better utilised.