I was wondering what the implication are when a server PHP version is upgraded from 5.6 to 7.
My ISP manages my dedicated server, and only use PHP5.6 at the moment (will upgrade only in one month) but I need to install Magento 2.1.x now (on PHP 5.6). Can I Setup my Magento site and then later let my Host upgrade the Server to PHP 7? Is that possible? Are there any issues I should be made aware of.?
You will not have any issues with upgrading from php 5.6 to php 7 if you only run Magento 2 on that server. We upgrade our hosted clients running Magento 2 from PHP 5.6 to php 7 all the time and do not see any problems.
I agree with Anton, it should be a seamless upgrade path. Just make sure the same pecl extensions are installed, the right php 7 features are enabled for M2, and possibly ioncube support for php 7 if you use any third party extensions that require ioncube support.
Also double check OpCode caching settings to make sure those are optimized as well.