I do believe that upgrading to rxjs@^5.5.x is inevitable. I suppose that we can introduce a breaking change along with the Angular@6 release.

I am not sure how we should proceed with the Angular LTS release. Probably we should also have 2 versions of the packages. What do you think?

The Angular 6 release will lead to another major version bump for all packages, but this is not directly related to the RxJS issue.

We need a fix for Angular 5.x LTS. It has been using RxJS 5.5 since it became available, but we didn't notice the issues as they only pop up when the build optimizer is enabled. The Angular CLI enables the build-optimizer by default in version 1.6.1 and later.

More bad news. Due to angular/angular-cli#9069, pipeable operators will include the full RxJS library.

Depending on your use case the difference can be quite significant. In my test project this adds around 100kB to the download size:

With global operators, RxJS ~ 52kB gzipped

With pipeable operators, RxJS ~ 125kB gzipped

With this in mind, the benefit from migrating to pipeable operators is lost. It makes more sense to wait for the bundling issue to be resolved. This might defer this fix to the Angular 6 release time frame.

My recommendation is to disable the build optimizer for the time being:
ng build --prod --build-optimizer=false

EDIT: See following response

Okay, so that was a bit rushed. The solution was to import individual operators:

import { map } from 'rxjs/operators/map'; instead of
import { map } from 'rxjs/operators';

Definitely following this one closely :-) #goteamtelerik

Is this being done as a break fix or is there a work around for the current kendo release? We implemented the latest kendo library and have a prod production date with it, but cannot do our prod build.

What previous version of the library will work?

@mikemwalsh it will be a breaking change, resulting in a major version bump. Otherwise we'll break users with rxjs < 5.5 that don't have pipeable operators.

The workaround is to disable the build optimizer:
ng build --prod --build-optimizer=false

All packages have been updated to use the new pipeable operators from RxJS 5.5+

This is a full list of the updated packages and their current version:

It's highly recommended that you update to these versions if your project is already on the latest rxjs. In addition, older versions will output a warning when used with RxJS 5.5:

WARN xxxx requires a peer of rxjs@^5 <5.5 but none is installed. You must install peer dependencies yourself.

As always, you can use npm outdated to inspect your project dependencies for updates.