The chargers will still work. Most, if not all, smartphones come with a basic AC adapter that has a USB port on it. You'll be able to buy a $3 cable that goes from male USB type-A to male USB type-C. Plug that into your old chargers and you're good to go. The biggest issue comes from car chargers as those often have a fixed cable with micro USB out. I solved that issue by purchasing a car charger that has a USB port but the ones that wireless stores often push aren't like that.
USB type-C won't be making its way into smartphone for a while. The next Nexus device will likely support it along with the Note 5 but that's pretty much it until a year from now when the next wave of flagship phones from Samsung, HTC, and LG are released. There's really nothing about USB type-C that would be beneficial with a smartphone except that the cable is reversible. Data transfer rates will increase but are they really a problem when using USB 2.0? Nope. You can also get video output using the same port but the advent of the $35 Chromecast makes that possible wirelessly (and likely costs just as much as a USB type-C to HDMI cable).
Get a new phone now if you need one. USB type-C isn't going to revolutionize the smartphone industry. It will make some things easier (like plugging your phone into its charger) but it won't drastically change anything. USB type-C is going to have a much bigger impact on the tablet and PC (notebook, ultrabook, and 2-in-1s) industries.