expand lts with upgrade decision guidelines

Author: yyx990803

src/lts/index.md

@@ -16,6 +16,22 @@ Vue 3 contains breaking changes that make it incompatible with Vue 2, so migrati
 
 Despite the breaking changes, the majority of Vue APIs are shared between the two major versions, so most of your team's Vue 2 knowledge will continue to work in Vue 3. In the long run, we also intend to avoid major breaking upgrades like the one between Vue 2 and Vue 3. Compatibility and ecosystem stability will be our topmost priority for future releases, and new features will be introduced in a way that does not require major migrations.
 
+
+### Upgrade or not to Upgrade
+
+Whether you should upgrade to Vue 3 highly depends on specific project details. Some general guidelines:
+
+1. Understand what you will gain from upgrading.
+
+   Due to 2.7, the DX gap between the two major versions are no longer that prominent - the main benefit of upgrading will be more refined TypeScript support, better performance, and access to the Vue 3 ecosystem and future new features.
+
+   Ask your team these questions: is the app stable and working well? Does the app expect continued new feature development into the future? Is there a pain-point / bottleneck that can only be solved by upgrading? If the app is stable and isn't experiencing major pain-point caused by Vue 2, then upgrading may not be worthwhile.
+
+2. Understand the cost of upgrading.
+
+   Does the app rely on 3rd party dependencies that are hard to be made Vue 3 compatible? Does the app rely heavily on changed behavior between Vue 2 and Vue 3? Can the team allocate dedicated time for upgrading? Spend some initial research time to gauge these aspects and come up with an estimation, then compare that to the expected gain from (1). We will not be able to provide a precise formula, but hopefully this can help with the decision process.
+
+
 ### Stay on Vue 2
 
 Some teams may not be able to upgrade to Vue 3 by this timeline due to limited bandwidth, budget, risk tolerance, or reliance on Vue-3-incompatible dependencies. We totally understand this, and want to ensure that staying on Vue 2 beyond EOL is a viable option.
@@ -34,7 +50,7 @@ For some teams, the main concern lies in security, compliance, and browser compa
 
 - You won't receive security fixes from EOL software. For the record, Vue 2 hasn't really had any real vulnerabilities in the past, but you may need a supported version to fullfil regulations or company policies.
 
-- If you are shipping your application to customers with SLAs. You *will* want to avoid including EOL software in your stack.
+- If you are shipping your application to customers with SLAs. You _will_ want to avoid including EOL software in your stack.
 
 - Browsers sometimes ship changes that break legacy libraries. This is extremely rare, but could happen in theory.