As TinCan is an upgrade of SCORM, can we consider the following as a fact: A system (LMS) that accepts TinCan objects should necessarily accept SCORM Objects? and If so, do we necessarily loose the tracking ability in this case, or we could configure SCORM's javascript to target an external LRS with tracking data?
Short answer: No.
Tin Can (officially named the Experience API) and SCORM are two unrelated standards. They are only related in ownership (ADL) and audience (e-learning developers).
Tin Can was designed for developers who were frustrated with the limitations of SCORM, including the requirement for the content to be hosted in an LMS. Tin Can does not require content to be hosted in an LMS.
Some Tin Can-based courses use SCORM-style statements for compatibility and interoperability (documentation), but there is no requirement for an LMS that supports SCORM to support Tin Can, or an Learning Record Store (LRS) that supports Tin Can to support SCORM.