Should we, who use SPServices, be concerned at all with Microsoft recommending not to use either the ASMX web services in SharePoint 2013 (http://msdn.microsoft.com/en-us/library/office/jj164060.aspx#DeprecatedAPIs) or the owssvr.dll (I used this one a lot when doing InfoPath stuff) for development purposes?
The Choose the right API set in SharePoint 2013 article is an important one, for sure. In it, there’s pretty clear direction about which API to choose based on the specific requirements of the solution you are building. As with anything, though, there’s a strong dash of “it depends”. It depends on things like your available skills, the device the code will run on, etc.
I would say that we should all be “cautious” rather than “concerned”. The SOAP Web Services are used by many parts of SharePoint still, with the most prominent being SharePoint Designer. If you sniff around in the traffic between processes, you’ll spot other places as well.
That said, deprecated is deprecated. If you build your solutions with the data access layer separated out from the business logic layer, you should be able to replace the calls if and when it becomes necessary.
I am not aware of any official specific time frames for the SOAP services going away, and the Product Group would need to give us a good, long lead time because lots of code depends on it, SPServices or not. Many people have built managed code-based solutions which use the SOAP Web Services as well. GetListItems is a workhorse operation no matter how you build your solutions.
There are many things you simply cannot do with REST yet, though in many cases CSOM may provide better coverage. If you are using SPServices for the operations which aren’t available in REST or CSOM, obviously you’ll want to continue doing so until there is a viable replacement. The REST coverage is improving steadily. (See Overview of SharePoint Conference 2014 and new content for developers for some information.) Keep in mind, though, that the majority of improvements will end up in Office365 first and in the SharePoint Server product at some point later or perhaps not at all. So your time horizons and cloud plans are also critical decision factors.
[If I had to put my money on a horse, it’d be REST over CSOM over the long term.]
All that said, if you are starting a new project on SharePoint 2013 of any significant size, you should be considering using the App Model, CSOM, and REST. SPServices may still fit in there somewhere, so don’t toss it out with the bath water just yet. I’ll continue evolving it as long as it has people wanting to use it. I think I still have plenty of things to do.