EDITED 3-18-2018 11:59 AM (CST) just to re-word it.
If you have a large capital gain in a future year, the unused capital losses can be applied to that gain (up to the amount of the gain or loss, whichever is less).
Yes, you are limited to $3,000 in losses per year if you no capital gain income to offset it.
Once it is applied against current capital gains up to $3,000 of the loss can be taken each year, until of is all used up.
Losses on your investments are first used to offset capital gains of the same type. So short-term losses are first deducted against short-term gains, and long-term losses are deducted against long-term gains. Net losses of either type can then be deducted against the other kind of gain. So, for example, if you have $2,000 of short-term loss and only $1,000 of short-term gain, the net $1,000 short-term loss can be deducted against your net long-term gain (assuming you have one). If you have an overall net capital loss for the year, you can deduct up to $3,000 of that loss against other kinds of income, including your salary and interest income, for example. Any excess net capital loss can be carried over to subsequent years to be deducted against capital gains and against up to $3,000 of other kinds of income.
See for more details: https://turbotax.intuit.com/tax-tips/investments-and-taxes/capital-gains-and-losses/L7GF1ouP8
