What will Microsoft be doing a year from now in regards to pricing and services? This really requires some clarity, because so far Win10 is not looking good from a privacy perspective IMO. It's not easy to recommend an upgrade right now with so much unanswered questions regarding data usage and price roadmap. What is their strategy after the first year?
Pricing for Windows 10 has been announced, $110 for Home and $199 for Pro. You have 1 year to upgrade for free, then you have a license for Windows 10 forever for that machine and you'll be supported for the lifetime of that device (as defined by Microsoft). If you don't upgrade within that year then you'd have to pay for the upgrade.