Although not offered by B&O you can upgrade the hard disk either yourself or the dealer. In both cases what you in essence do is making a low level copy of the hard disk on a new larger disk so all the software is preserved. Please be aware that the overall power of the system is limited (processor/memory) so I do not know how well it will work with extreme large libraries (although I do not foresee issues).
Than the harder questions; do you buy again
Sincerely I do not know. I use the system a lot. Is works fine, looks great and in general it is a pleasure to use. However there are a few things I do not like. Most of them are software related and one hardware As I wrote earlier, I would have loved it, when I could slid in a cd in [the BS5] as well.
I have a lot of classical work on the my disk and I dislike the limited opportunities to to sort and access these on the BS5, putting in a cd is much easier/nicer in such cases. Also when a friend is passing by with a new cd, ripping and putting it on the BM5 is a bit overkill...
From a software perspective I really dislike the limited use of metadata. I have properly added all kinds of metadata to my music and I would like to use this metadata for sorting and selecting music. Currently I have nearly 500 albums on the BM5. If I would like to play music from a specific genre or componist/performer/... I can not use the BS5 for selecting on something else than Album title or Artist. Another thing is cooperation between Beo4/Beo5 and the BS5/BM5, skipping numbers/skipping albums is not how I would like it (more standard CD player approach). The way the favorites function works is awfully although this is partly due to the rudimental integration between the BM5 and the Apple computers I use. And so there are a bunch of smaller things as well.
So my advice would be, check the system out at the shop. Have a look at the your music collection, you habits for listening to your music, going through it and see how your usage fit within the capabilities of the system. If you like it Buy if not, wait for upcoming software release