I think that is exactly how any altcoin behaves in manipulation-free times.
This doesn't automatically grant you a BAM!
The slow decay can go on for an indefinitely long time until some internal or external change (bad or good news from either the developers or other big players through trolling or praising articles/forum posts/etc, organized/engineered pump&dump cycles, and so on) triggers a frenzy (panic sale or panic buy, rapid movements with big volumes).
Darkcoin can't possibly end up like that any time soon because it will be far from boring or forgotten for long but decays like this can go on until the last exchange removes the coin and the last sad guy/girl deletes the last wallet.dat in existence and thus the coin officially dead. This is the realistic future of almost every altcoins in the not so far future, especially of true shitcoins.