If someone is late to the mining game, it doesn't mean the concept of a digital currency is a lost cause, it just means that they lost their chance to be among the early adopters who got the highest return on their investment. Bitcoin is an idea, and a new medium of exchange bypassing the negative ROI that is fiat currency. Losing interest in bitcoin because the ability to mine for yourself is becoming less profitable, is like saying that people wouldn't use or invest in gold because they lost their chance to start a gold mining company.
Not to mention the fact that if it does increase in popularity and make its own niche into mainstream usage, then some of the predictions of increase in value (that are fairly well researched and thought out such as this for example http://www.youtube.com/watch?v=K7LQu-eIOO0) it would still give people who are buying and using them now, quite a good ROI in the long run, even if the true value 5 years from now falls well short of some of these predictions...