.NET 4.5 offers lots more advantages and v2 when I start it for my FYP will be based on .NET 4.5. I will of course keep Win Toolkit v1.5 available for XP users and will only do bug fixes for it. So just to summarize:
Win Toolkit v1.4.x.x will remain available requiring .NET Framework 3.5 Win Toolkit v2.x.x.x will be on a separate download page and will require .NET Framework 4.5 I remember when I first started Win Toolkit on .NET 2.0 when 3.5 was available. I'm now on 3.5 whilst 4.5 is available and for once would like to jump to the latest and take advantage of all of its features. Especially when it comes to multi-threading.