If Satoshi is dead, he will become a symbol or even a legend with time

But he is likely already a legend, and even more so if no one finds out about him. Though this is unlikely, there should be folks who know for certain who is the guy behind this name, and they will make a clean breast sooner or later (when their time comes). Regarding the questions in the OP, Bitcoin technology is not tied to just one person (in other words, there's no single point of failure), so everything will go on as per usual. The market sentiment can be confused, though. On the one hand, his coins would be essentially left for dead, which would mean the fears of them being dumped will vanish over time (provided there were any, in the first place, of course), while on the other, the markets may feel somewhat depressed and some folks may choose to dump their coins (but not many, anyway). The community won't be quite happy, obviously. I guess the majorly would prefer if Satoshi remained incognito till the end of days (or at least, till the end of Bitcoin)