I will give some of them a "stab in the dark"....
Q - SAP Fiori rolled-out 9 HCM Apps so far, and around 500+ for other non-HR modules. What is this trend telling HR customers?
It tells us exactly what we have known for a while....SAP's focus for HCM is now SuccessFactors and little is/will be done around on-premise HCM. At the TechEd 2015 keynote in Vegas, there was even a slide that said "*Note: HCM default = SuccessFactors Employee Central". Fiori apps are very focused (for now) on on-prem.
Q - Webdynpro ABAP based services are not supported via Fiori launchpad. If it is true, we have to do dual development ( means for each Webdynpro for ABAP services, we may need to build UI5) - How UX360 add value here ....
You are talking about VERY different applications. WDA apps are more "heavy" and now "device friendly". Fiori apps follow a much "simpler" paradigm and are more purpose built to a single task as well as being "light weight". However, I don't think there is antyhing that would keep you from "launching out" to a WDA if you needed/wanted too. I can better see the scenario of launching "out" to your Fiori app from your HR Renewal landing page than doing it the other way around.
Q. What are the Pro`s and Con`s for Unified platform?
When there truly is a "unified" platform, I will let you know. haha
Q: What will be the landscape architecture?
We have SAP Gateway/ Deploy SAP Fiori Add-ons to ECC/ Gateway Sandbox. Planning to Deploy HR-Renewal 2.0.
That is pretty much it.
Q : Where will be the unified launchpad will exist? in SAP Gateway or ECC. BTW we have implanted SAP Gateway Hub Architecture.
Not sure what you mean here....where it will "exist"....it depends which way your "point of access" will be....through the Fiori Launchpad or your HR Renewal landing page?