Hi Aislan,
What exactly do you mean with "Java for Web"? The Web Profile of Java EE 6 and above? On the server side, that would come to mind.
There is almost no "Web aspect" to Java SE. Applets or Java Web Start (I trust you don't mean that, because it is more or less the only thing that will be removed with JDK 11 or 12)
What has been there will either be removed soon or already has. These are in Java EE/Jakarta EE and some that were taken for granted in Java SE like XML probably have to be added to certain Jakarta EE modules.
Starting with Java 11 this fall there will be LTS releases. And it is up to vendors and implementors of Jakarta EE compliant products, but it is safe to assume that enterprise offerings (like JBoss EAP or whatever it may be called in future?) are based on a certain Java SE LTS version. As the first Jakarta EE release is not expected before early 2019 that is likely what some vendors may use already, as long as there are no major incompatibilities or issues compared to Java SE 8.
I doubt, the shorter release-cycle has that much impact on how many people will use Java and Jakarta EE for Enterprise and Web/Cloud projects. If there is a reduction, it may be because of other languages being equally or sometimes more attractive to certain groups of developers. Look at Oracle Code One replacing JavaOne where in total there seem to be a lot less Java talks in the program, even though the total number of sessions could be larger, but Java is just one of several languages, the way other big developer conferences like DWX (Developer Week, one of the largest in Germany with ~2k attendees last month) or Codemotion (~30k attendees across all host cities, Java playes a minor role and even none in some of them) already practice. And what others like DevoXX also do, let alone the name change it had to undergo long before Oracle dropped the Java from its JavaOne.
Kind Regards,