You can look at this in two ways:
- 2018 won't be crucial year of bitcoin if we are talking overall and taking into consideration time in future that is yet to come

- 2018 could potentially be crucial if we look only time till now

If 2018 don't bring good to bitcoin, it will surley bring good to altcoins as there are many people entering the scenes and we are seeing exchanges having tons and tons of new accounts that are being open.