One big learning of mine from SuiteWorld 22 is that NetSuite is not yet ready to migrate bundles to SuiteApps, so there will be no requirement anytime soon to convert. However, they also confirmed that if your bundle objects are supported by SDF, it will be better for you in the long run to build a SuiteApp for go-forward with new customers, and keep legacy in place until a conversion is viable. The critical issue comes when attempting to ‘uninstall’ the existing bundle, which will remove the existing objects and data… which is not viable. It is a complex problem, which will take time/resources to resolve, and it’s one of many things to do… Some suggestions were to build a ‘break bundle’ type of feature to allow a transition of ownership from bundle owner to APP ID Owner, assuming they’re the same, etc, but that would still require that all bundle objects were supported by SuiteApp SDF, which is still on the roadmap.

if we get a native support from NetSuite would be great, there are some custom records which has millions of record entries, even if we think of doing a CSV approach there are some linked record which have got inactive over time

The transition from the NetSuite Connector bundle to the SuiteApp did involve a delete of the fields. Their solution was to download all data in those fields and re-import. Fortunately, we didn't have anything critical that needed replacing, but it's not an elegant solution by any means. Hopefully a 'keep these' could be designed in.