You are lucky, there isn't a lot of change between 100-101 and 100-105. Keep going with your book, make sure you check the blueprint to see if you need to study something not covered in the book, and you should be fine. The 100-101 book will get you about 99% of what you need to know.
For ICND2, make sure you get the 200-105 book because there are lots of changes.
Does that mean for someone taking ICND exams 1 and 2 that until Aug 20 and Sep 24 respectively, they have a choice of taking either v2.0 or v3.0 of both exams?
Yep, you can choose right now if you want to go for v2 or v3. Until the cutoff date, you can do whichever one you choose. You could even do ICND1v3 and ICND2v2 if you'd like.