Hopefully, if you work for a publicly traded company, you are already in production with RAR (ASC 606 & IFRS 15). MEAs (Multi-Element Arrangements) can be challenging. If you're a private company, get started NOW, if you haven't already - it takes longer than you might think.
For Leasing, you have until December for ASC 842 and January 2019 for IFRS 16, if I recall correctly. Again, private companies get an additional year. Leasing does not seem as complex as RAR has been, but I'm expecting challenges interfacing 3rd party apps with SAP.