Every 10 minutes a block is mined for 25 BTC. 25 coins per block, 6 blocks per hour, 24 hours per day, 365 days per year = 25 * 6 * 24 * 365 = 1,314,000 new BTC each year.
That means in the next 1 year, at these levels, there is a supply increase of ~10.3%.
Block reward will be 25 BTC until 2016. For the Bitcoin price to increase, the market cap must increase at a rate higher than the supply of new coins.
In other words, for your 1 BTC to be worth the same price it is today, one year from now, the Bitcoin market cap must increase 10.3% in the next year.
So yes, the OP has a good point. Many people do not realize that for their Bitcoin investment to increase in value, the overall market value of Bitcoin must increase over 10% over the following year.
Right, then why did the value of bitcoin explode while the block reward was double the reward of what it is now? And there were less bitcoin back then so the percentage of bitcoin added daily was much higher than it is now.