Even if, (and that's a big "if") Bitcoin where to stay on top, Bitshares has a lot more to offer besides sending transactions, things BTC won't be able to do. The biggest example of this is the DEX (decentralized exchange).
If Bitcoin where to fall in a manner where it goes down drastically, yes it might cause some panic and alts will go down. But just as well will the market cap that was previously in Bitcoin, be pumped into those alts in due time.
Not disagreeing with you, just noting that "in due time" will mean a long time. Best to buy with cash and HODL; that way, you can wait years if you have to (or want to.)
HODL'ing for years has always been my plan ;) Though I expect this year to be a major boost when it comes to Bitshares. A lot of businesses are currently working on intergrating into the Bitshares blockchain. I also believe this year to be the beginning stage of the shift where the utililty will be set on the first place.
Good for you: I really mean that. Don't think in terms of days or moths: think in terms of years.
Related:
https://steemit.com/blocktivity/@theguruasia/what-blocktivity-says-today-steem-hodl-the-top-and-bitshares-is-rising-tga-analysis-16-01-2018