Predict interface names starting from ubuntu 15.10

As mentioned here since Ubutnu 15.10 there are some different naming schemes for network interfaces supported:

• Names incorporating Firmware/BIOS provided index numbers for on-board devices (example: eno1)
• Names incorporating Firmware/BIOS provided PCI Express hotplug slot index numbers (example: ens1)
• Names incorporating physical/geographical location of the connector of the hardware (example: enp2s0)
• Names incorporating the interfaces's MAC address (example: enx78e7d1ea46da)
• Classic, unpredictable kernel-native ethX naming (example: eth0) - depreciated

I am writing a script that takes interface name with grep:

if_name=$(ls /sys/class/net | grep "en")

and then changes it to eth. I've tested script on a few machines and it was fine, but is there a chance that interface name now can start from another letters and my command above won't work? And if so, are there any better alternatives?

Ok, I found out here that two character prefixes based on the type of interface:

 *   en -- Ethernet
 *   sl -- serial line IP (slip)
 *   wl -- wlan
 *   ww -- wwan

Also, the best way to find out you primary interface name:

route |grep default |awk  ' {print $8} '