***UPDATE*** Microsoft announced that InfoPath 2013 is the last release of the desktop client, and InfoPath Forms Services in SharePoint Server 2013 is the last release of InfoPath Forms Services. See the Update on InfoPath and SharePoint Forms. Definitely take a look at Nintex Forms as a potential replacement.
I ran across this interesting post from Andrew Connell entitled My Thoughts: InfoPath 2013 & the Future of InfoPath. Great insight and thoughts about the future of InfoPath and where Nintex Forms fits in.
I get asked by clients frequently if Nintex Forms is a replacement for InfoPath. In my opinion, Nintex Forms is not trying to replace InfoPath. There is functionality that both offer (validation, BCS integration, repeating groups, edit/view in browser), but there are things that Nintex Forms does that InfoPath does not (mobility options, anonymous user consumption, workflow integration, browser-based designer) and vice versa (direct database access, call web services, nested repeating groups). If you have Nintex Workflow, then Nintex Forms is an amazing complimentary product that helps you extend your workflows.
TechRhodes 
NIntex forms cannot be used on form libraries. I think this is the major drawback of Nintex forms.
True. Nintex Forms can not be used in a forms library. That’s due to the nature of what a forms library actually does, which is store data in XML files as an item in the form library. Nintex Forms are used as front end data collection and editing forms for storing data directly in a list or library.
Looks like we have our answer. InfoPath 2013 and InfoPath Forms Services in SharePoint Server 2013 is the end of the line.
http://blogs.office.com/2014/01/31/update-on-infopath-and-sharepoint-forms