1. The majority of manual testing positions will be eliminated in software industry. It is happending in Silicon Valley, and it will spread to other areas. One should be prepared on how to deal with it. For those 老奶奶們, they may get retired then.For the young and middle-aged QAs who can't code, it will be very tough.
For example, we never hire QAs who can't code. They don't need to code as good as developers, but they should be able to write automation tests once they are provided a testing framework. For those QAs who can't code and who were hired before the transition, I can't see they have any career in the QA field. A good autmation QA can be more productive and, most importantly, more reliable than at least 5 manual testers. There are no reasons that companies will continue hire manual testers.
Some become very good custom support people, though, if they are good at communication, since QAs know the products very well and compared to most custom supports, they have some technical background.
2. Many developers transit to QAs. Usually these QAs are the best ones. First they can write code. Second, they have received some training in development. So they communicate with developers better. Third, they understand the whole engineering process much better and have a better look at the big picture. This is required for any good QA managers.
Speaking frankly, developers don't want to be QAs. We all know the reasons. This actually provide an excellent opporunity for not-so-good developers. A very good QA is actually as hard to find as a good developers. Good QAs are paid very well, better than average developers.
3. For you, you can try "在這公司level II software混個幾年,學點東西,再跳槽". You can always jump back to QA. Your developer experience will be very valuable in your career. Think about it. Imagine the scenario that developers are frustrated about most QA's inability to produce comprehensive test plans and reliable testing codes and the inability to understand what developers want. At this moment, if you can talk with developers with their language, show you understanding on the whole engineering process, developers will love you. If you are good at communication, you will be promoted in no time. This is what "長期來看更有發展前途" means.
You already have a CS degree. Maximize it to gain advantage in your QA career. Who knows. It is possible that you are very good in programming. Anyway, you can always jump back.
4. You must be motivated, though. "我懶惰" will not work out for a developer. If a hard-working 5-years can make a much better long term career, I think it is a good deal. If your company provides training and is patient for entry-level developers, it will be a very good opportunity. Working with "高手" is the fastest way to improve oneself.