Does "Reasons for Allowance" imply that there is a high probability of this application to be granted in the near future.
37 CFR § 1.104(e) provides:
If the examiner believes that the record of the prosecution as a whole does not make clear his or her reasons for allowing a claim or claims, the examiner may set forth such reasoning. The reasons shall be incorporated into an Office action rejecting other claims of the application or patent under reexamination or be the subject of a separate communication to the applicant or patent owner.
Thus having a standalone reasons document strongly implies that no further office action will be issued, otherwise the reasons would be incorporated into that. This means that the application is generally in order for allowance.
A further gloss is provided by MPEP § 1302.14:
One of the primary purposes of 37 CFR 1.104(e) is to improve the quality and reliability of issued patents by providing a complete file history which should clearly reflect, as much as is reasonably possible, the reasons why the application was allowed.
In other words, the reasons for allowance are generally provided when the application (and not just certain claims) is allowed.
If yes, what is the time line that we are looking at?
I couldn't find a precise timeframe, so the best I could suggest is "soon".
MPEP § 1302.03 provides:
In all instances, both before and after final rejection, in which an application is placed in condition for allowance, applicant should be notified promptly of allowability of the claims by a Notice of Allowability PTOL-37.
If there are no formal matters outstanding, you would receive a notice of allowance instead.
Once you receive the notice of allowance, there are some formalities that occur before the application is issued (granted). Notably, you must pay the issue fee within 3 months of the notice of allowance. The application will then issue around 2 months from paying that fee.
Per MPEP § 1309:
When the issue fee is paid and all other requirements have been met (e.g., drawings) for issuance as a patent, the application is then electronically exported to the Final Data Capture (FDC) stage. The FDC makes any updates necessary to the electronic file and places the allowed patent application in an issue. The average time that an allowed application is in the FDC process is 5 weeks (2 weeks of processing time for assignment of issue date). The "Issue Notification" is mailed approximately 3 weeks prior to the issue date of the patent.