MariaDB Server 10.2 will not ship with Percona XtraDB at all, but only with Oracle InnoDB.
However, XtraDB was the built-in InnoDB implementation in MariaDB Server 10.0 and 10.1.
To ease upgrades, InnoDB in MariaDB Server 10.2 should accept the XtraDB options that were available in 10.1, and display warnings about them. Here is a list obtained with

diff -u <(sed -ne 's/^  MYSQL_SYSVAR(\(.*\)),/\1/p' storage/xtradb/handler/ha_innodb.cc|sort) <(sed -ne 's/^  MYSQL_SYSVAR(\(.*\)),/\1/p' storage/innobase/handler/ha_innodb.cc|sort)|grep '^-[a-z]'

-adaptive_hash_index_partitions

-additional_mem_pool_size

-api_bk_commit_interval

-api_disable_rowlock

-api_enable_binlog

-api_enable_mdl

-api_trx_level

-buffer_pool_populate

-cleaner_eviction_factor

-cleaner_flush_chunk_size

-cleaner_free_list_lwm

-cleaner_lru_chunk_size

-cleaner_lsn_age_factor

-cleaner_max_flush_time

-cleaner_max_lru_time

-corrupt_table_action

-empty_free_list_algorithm

-fake_changes

-file_io_threads

-foreground_preflush

-kill_idle_transaction

-locking_fake_changes

-log_arch_dir

-log_arch_expire_sec

-log_archive

-log_block_size

-log_checksum_algorithm

-max_bitmap_file_size

-max_changed_pages

-mirrored_log_groups

-priority_cleaner

-priority_io

-priority_master

-priority_purge

-sched_priority_cleaner

-sched_priority_io

-sched_priority_master

-sched_priority_purge

-show_locks_held

-show_verbose_locks

-stats_include_delete_marked

-track_changed_pages

-track_redo_log_now

-use_global_flush_log_at_trx_commit

-use_stacktrace

-use_sys_malloc

Some discretion could be used. The innodb_api* settings never did anything useful in MariaDB, and they were removed in MDEV-12050 along with the unused Memcached hooks.

innodb_additional_mem_pool_size and innodb_use_sys_malloc can be removed, because they were deprecated in Oracle MySQL 5.6 (thus, MariaDB 10.0 already) and removed in 5.7.

innodb_adaptive_hash_index_partitions was implemented in MySQL 5.7 as innodb_adaptive_hash_index_parts. We should have an alias for that.

The Percona setting innodb_log_checksum_algorithm (a choice of values) was replaced by the Boolean innodb_log_checksums (offering CRC-32C or none). We could map the value "none" to OFF and everything else to ON.

The remaining parameters look like Percona additions which we can choose to ignore (issuing a warning). Perhaps some features could be ported from Percona 5.7.