Is having duplicated content on different domains a problem when using alternate tag, but no canonical?

[lcourse]

We will be launching a couple of new language versions.

I understand that ccTLD is mostly considered as best option, however I thought that to start with it might be better to launch the new language version first on a subdirectory of our established domain with strong backlink profile as it may rank much better until I can attract some strong links to new ccTLD.

I would wait for the pages of new language versions to be indexed on the main domain and then after a month launch the same content paralell on the ccTLD setting up an alternate tag in the main domain pointing to the ccTLD. I would not setup any canonical tag. As I understand google would rank whatever of the 2 versions ranks higher.

Should not cause duplicated content issues right?
Any thoughts?

EDIT:
For clarification. The language we are launching are mostly spoken in several countries. E.g. for Portuguese I would add in main domain an altnernate tag for Brazilian visitors to Brazilian ccTLD, but no alternate tag for Portuguese visitors. For Corean I would add in main domain an alternate tag for visitors in south corea, but not one for visitors in north corea.

[gfiorelli1]

If you with alternate mean rel="alternate" hreflang", then your intuition is correct.

More over, the rel="canonical" of the URLs with the hreflang implement MUST be always self-referential, in order to no create conflict with the rel="alternate" hreflang (i.e.: Snippet identical to one site, URL of another site)...

[lcourse]

Gianluca,
thanks again.
yes I meant  rel="alternate" hreflang.

regarding canonical so if I understood well what you are suggesting is that canonicals should point to same page on same domain and should not point to pages on other domains

domain.com/pt should have canonical to domain.com/pt

domain.com.br should have canonical to domain.com.br

[gfiorelli1]

Exactly